Rosetta - Post Separation Ops at Comet 67P C-G, November 14, 2014 - |
Rosetta - Post Separation Ops at Comet 67P C-G, November 14, 2014 - |
Nov 27 2014, 12:48 AM
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#31
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Member Group: Members Posts: 166 Joined: 20-September 05 From: North Texas Member No.: 503 |
... the jets are primarily pointing toward the Sun, while a comet's dust and ion tails point away from the Sun. Can Rosetta observe the process by which the trajectory changes as they become tails, or is Rosetta too close to see that effect? Absent any atmosphere, there is no air friction to slow down the jets at they stream outward from the surface. My guess is that as the comet's surface heats up (on the sun-ward side) the jets would be streaming directly away from the surface, or towards the sun. It would only be when the comet falls deeper into the sun's gravitational well, and picks up speed, that the tail is "left behind". I await someone more knowledgeable about comets to correct me. |
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Nov 27 2014, 01:16 AM
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#32
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Solar System Cartographer Group: Members Posts: 10226 Joined: 5-April 05 From: Canada Member No.: 227 |
-------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Nov 27 2014, 01:16 AM
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#33
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Senior Member Group: Members Posts: 4256 Joined: 17-January 05 Member No.: 152 |
My understanding was that it was the pressure of the solar wind that forms the tail(s). So heating on the sun facing side leads to jets towards the sun, which eventually are deflected by the solar wind to form the tail.
If there were no solar wind, particles in a jet pointing towards the sun would presumably get ahead of the comet rather than be left behind (at least prior to perihelion). Edit: Phil beat me by less than a minute! |
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Nov 27 2014, 03:52 AM
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#34
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Member Group: Members Posts: 267 Joined: 5-February 06 Member No.: 675 |
Thanks for the comments and for Phil's good link. The question remains, however, of what details Rosetta will be able to provide about the process changing jets emerging on the sunward side of the nucleus into tails streaming away from the Sun.
Steve M |
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Nov 27 2014, 11:28 AM
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#35
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
Small grains should be more susceptible to solar wind and radiation.
The GIADA instrument should be well-suited to investigate this question in very detail: QUOTE GIADA (Grain Impact Analyser and Dust Accumulator) will measure the number, mass, momentum and velocity distribution of dust grains in the near-comet environment. Giada will analyse both grains that travel directly from the nucleus to the spacecraft and those that arrive from other directions having had their ejection momentum altered by solar radiation pressure.
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Nov 27 2014, 01:55 PM
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#36
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Member Group: Members Posts: 267 Joined: 5-February 06 Member No.: 675 |
GIADA should provide interesting velocity data. Look forward to more GIADA insights into dust particle trajectories since since this early detection of a few dust particles.
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Nov 29 2014, 08:58 AM
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#37
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Member Group: Members Posts: 819 Joined: 3-June 04 From: Brittany, France Member No.: 79 |
NavCam mosaic of 26 November. The rotation of the comet has been substantial in the twenty minutes that passed between the two lower images, resulting in artifacts in the stitching process.
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Dec 5 2014, 09:11 PM
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#38
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Member Group: Members Posts: 146 Joined: 22-November 14 From: Bormida (SV) - Italy Member No.: 7348 |
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Dec 5 2014, 09:28 PM
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#39
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
Beautiful. Thanks for sharing that. It's amazing to pan around that view. What a place!
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Dec 7 2014, 01:13 AM
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#40
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Junior Member Group: Members Posts: 23 Joined: 15-February 14 Member No.: 7141 |
Lovely mosaic eliBonora! The one on the ESA blog has a blurry seam, where the foreground and background limbs meet, that had me scratching my head until I saw yours
Here are a couple attempts at anaglyphs from the Dec 1st and 2nd NAVCAM images, made from the slices where the bottom two (foreground) images overlap. Some artistic liberties have been taken to account for areas which were shaded in one image and lit in the other. |
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Dec 8 2014, 04:44 PM
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#41
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Member Group: Members Posts: 146 Joined: 22-November 14 From: Bormida (SV) - Italy Member No.: 7348 |
Lovely mosaic eliBonora! The one on the ESA blog has a blurry seam, where the foreground and background limbs meet, that had me scratching my head until I saw yours Thank you Dan. Nice anaglyphs. I think the difference is that we combine these comets by hand and we don't use the software's blending option. -------------------- |
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Dec 10 2014, 09:42 PM
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#42
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Member Group: Members Posts: 819 Joined: 3-June 04 From: Brittany, France Member No.: 79 |
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Dec 11 2014, 05:33 PM
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#43
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Solar System Cartographer Group: Members Posts: 10226 Joined: 5-April 05 From: Canada Member No.: 227 |
The latest Navcam blog shows new - or apparently new - features in the neck. Here's a comparison between October and December images (December on the right). I would suggest a close examination of images would probably show more things like this.
Phil -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Dec 11 2014, 07:51 PM
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#44
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Solar System Cartographer Group: Members Posts: 10226 Joined: 5-April 05 From: Canada Member No.: 227 |
Sure enough, here's a comparison between 24 September and 9 December with the new feature on 9 December noted. Differences in lighting and resolution are small enough that I think this is a real change.
Phil (PS... must work on book... must work on book... aaaargh!) -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Dec 11 2014, 09:44 PM
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#45
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Member Group: Members Posts: 404 Joined: 5-January 10 Member No.: 5161 |
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